Week of March 31

Week of March 31

On April 1, 1968, the last fighting of the Communist Tet Offensive subsided as the U.S. Army 1st Cavalry Division and the U.S. Marine Corps 3d Division commenced Operation PEGASUS. The joint force’s objective was to reach and relieve the Marine garrison at Khe Sanh, which had been under attack from surrounding North Vietnamese Army forces since January.

The Khe Sanh Combat Base, atop a hill in northwestern South Vietnam, guarded a crucial infiltration route across the Laos border. Communist personnel had long used this route to bring supplies and reinforcements into the military region known as I Corps. In early 1968, roughly 6,000 Marines manned Khe Sanh (approximately 3,000 inside the hilltop base itself) along with a contingent of South Vietnamese Army rangers.

Approximately 30,000 North Vietnamese forces laid siege to Khe Sanh in January 1968, quickly cutting it off from ground reinforcement and resupply. For a time, allied leaders were convinced that the battle for Khe Sanh would be the pivotal battle of the war. However, as the Tet Offensive kicked off at the end of January, it became clear that the siege of Khe Sanh was partially a diversionary attack.

In a sense, the diversion worked, though not in the way the North Vietnamese had likely hoped. The attack on Khe Sanh did not draw significant numbers of U.S. troops away from their stations further south. But the fierce and sudden beginning of the Tet Offensive did prevent U.S. commanders from mounting a relief operation. Nevertheless, the Marines at Khe Sanh, with the help of artillery and air support, managed to hold their position against vastly superior numbers for over 10 weeks.

By the end of March, with the last of the Tet attacks defeated, allied commanders turned their full attention toward relieving the Khe Sanh defenders. The relief operation, codenamed PEGASUS, commenced on April 1. Commanded by Army Major General John J. Tolson, elements of the 1st Cavalry Division were joined by two battalions of Marines and two battalions of South Vietnamese Army soldiers—approximately 30,000 men altogether.

To begin, U.S. Army and Marine engineers and a group of Navy Seabees completed a forward operating base named Landing Zone Stud off Route 9. They finished the base in fewer than 11 days—complete with a 500-foot airstrip, operation and communication centers, ammunition depot, and refueling points. Meanwhile the 9th Cavalry conducted reconnaissance-by-fire along the planned route of advance for 6 days, eliminating North Vietnamese antiaircraft positions with air assaults. U.S. Air Force B-52s bombarded North Vietnamese strong points in the area as well.

After a diversionary feint toward the North, the combined PEGASUS force began to clear Route 9, the primary road leading to Khe Sanh, of enemy forces. Proceeding westward, they executed a series of ground and airmobile assaults that eliminated North Vietnamese positions along the road. At each newly-established landing zone, 1st Cavalry forces erected additional fire bases, providing further artillery support for both PEGASUS and the Khe Sanh Marines.

By early April, roughly half of the besieging Communist forces had withdrawn, leaving a single North Vietnamese division, supported by two tank companies and multiple antiaircraft units, to continue harassing the combat base. Despite having endured months of ferocious artillery and ground attacks, the Marines at Khe Sanh declined to simply wait for PEGASUS to reach them. A contingent of the Khe Sanh defenders broke out on April 4, meeting heavy resistance but managing to take Hill 471 overlooking the base. Another Marine brigade attacked eastward in the direction of PEGASUS forces. The two elements finally met on April 8, when the 2d Battalion, 7th Cavalry linked up with the Marines, ending the siege. The North Vietnamese troops still surrounding Khe Sanh pulled back into Laos, and allied units cleared out remaining pockets of enemy troops until April 15, when Operation PEGASUS ended. According to U.S. Military Assistance Command Vietnam, PEGASUS forces inflicted nearly 1,400 fatal casualties on the North Vietnamese Army. At least 92 Americans were killed in the operation, with another 667 wounded and 5 missing. A total of 33 South Vietnamese soldiers also died in the relief operation.

The success of PEGASUS meant that after over three years of war, U.S. troops had still not lost a single significant battle in Vietnam. Despite this, it grew harder and harder to envision a path to victory. U.S. casualties mounted, American public opinion swung against Lyndon Johnson’s handling of the war in the wake of Tet, and the North Vietnamese showed no signs of weakening resolve.1

1Graham A. Cosmas, United States Army in Vietnam: MACV: The Joint Command in the Years of Withdrawal, 1968–1973 (Washington, D.C.: Center of Military History, 2006), 116; Jack Shulimson, et. al., U.S. Marines in Vietnam: The Defining Year, 1968 (Washington, D.C.: U.S. Marine Corps History and Museums Division, 1997), 241, 281, 283–86, 289–90; Spencer C. Tucker, ed., The Encyclopedia of the Vietnam War: A Political, Social, and Military History (2nd edition; Santa Barbara, CA: ABC-CLIO, 2011), 887–88.

Operation PEGASUS Map


3. Sketch map of Operation PEGASUS between April 2 and April 4, 1968. LZ Stud was the name of the forward base that Army, Marine, and Navy engineers constructed in just 11 days at the end of March 1968. (U.S. Army Center of Military History)